A pressure sensor that utilizes a change in electric capacitance in accordance with a deformation of a diaphragm is disclosed as a differential pressure sensor measuring a pressure fluctuation (see, for example, Patent Literature 1). The pressure sensor disclosed in Patent Literature 1 forms a hollow in an auxiliary layer covered by a diaphragm layer through pores in the diaphragm layer, and such pores are air-tightly closed without causing a part of a block-off layer on the diaphragm layer to be filled, thereby letting a diaphragm to have a desired deformation performance.